JP2006006067A - Brushless dc motor driving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brushless DC motor driving apparatus for reducing a switching loss in comparison with a sinusoidal wave and improving a utilization rate of an induced voltage. <P>SOLUTION: A trapezoidal wave that can conduct 120-degree enegization on the basis of periods and timing of rotational pulses from three hall ICs disposed in the vicinity of a stator is generated. PWM control is implemented on the basis of the trapezoidal wave. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drive device that controls a brushless DC motor by an inverter circuit.

The driving method of a brushless DC motor (hereinafter simply referred to as a motor) detects the rotational position of the rotor using a position signal from the Hall IC that detects the position of the rotor and an induced voltage of the stator winding. PWM control is performed based on the detected rotational position and a speed command signal from the outside, and the rotation is controlled by supplying drive current to the stator windings from each switching element of the inverter circuit (for example, see Patent Document 1). ).
JP 2004-23823 A

  In order to increase the efficiency of the motor, there is a method of increasing the utilization rate of the induced voltage on the drive circuit side. When performing this method, from the viewpoint of the utilization factor of the induced voltage, when the magnetization of the rotor magnet of the rotor is a sine wave, the drive method is preferably a sine wave energization method. However, when sine wave drive is attempted by the PWM control method, the upper and lower switching elements of the full-bridge inverter circuit are always turned ON / OFF to perform PWM control, resulting in higher switching loss and higher efficiency as described above. This is a contradictory result.

  Moreover, since the utilization rate of the induced voltage is low at 120 degrees energization, this also becomes a problem in increasing the efficiency of the motor.

  Therefore, in view of the above problems, the present invention provides a brushless DC motor driving apparatus that can lower the switching loss than a sine wave and increase the utilization of the induced voltage.

  According to a first aspect of the present invention, there is provided an inverter circuit for supplying a driving current to the three-phase stator winding of the three-phase brushless DC motor, and a rotation speed detection for detecting the rotation speed of the rotor of the brushless DC motor. In the brushless DC motor driving apparatus, the control device includes: a control means for outputting a control signal to the inverter circuit based on a speed command signal from the outside and a period of a rotation pulse from the rotation speed detection means; The means generates an energization circuit that is a rectangular wave based on the period and timing of the rotation pulse, and generates a rising ramp wave and a falling ramp wave based on the period and timing of the rotation pulse. The trapezoidal wave generating means, the rising ramp wave, the energization wave, and the falling ramp wave are synthesized and are generated by the speed command signal. A trapezoidal modulated wave generating means for generating a trapezoidal wave by determining a triangular wave oscillation circuit that oscillates a triangular wave at a predetermined period, a PWM modulation circuit that generates a PWM modulated wave from the trapezoidal wave and the triangular wave, A brushless DC motor drive device comprising: a drive circuit that generates the control signal based on a PWM modulated wave.

  The invention according to claim 2 is characterized in that the rotor magnet of the rotor is magnetized so that the induced voltage of the rotor of the brushless DC motor becomes a trapezoidal wave. It is a drive device of a DC motor.

  The invention according to claim 3 is the brushless DC motor drive device according to claim 1, wherein the energization circuit conducts 120-degree energization, 150-degree energization, or 180-degree energization.

  The invention according to claim 4 is the brushless according to claim 1, wherein the rising slope wave and the falling slope wave have a width of between 10 degrees and 60 degrees, respectively. It is a drive device of a DC motor.

  According to a fifth aspect of the present invention, the rotation speed detection circuit has a position detection element in the vicinity of a rotor of the brushless DC motor, and detects the rotation speed based on a position signal from the position detection element. The brushless DC motor drive device according to claim 1.

  The invention according to claim 6 is characterized in that the rotational speed detection circuit detects an induced voltage of each stator winding and detects the rotational speed based on the detected induced voltage of each phase. A brushless DC motor driving apparatus according to claim 1.

  In the brushless DC motor drive device according to the first aspect of the present invention, a trapezoidal wave is generated based on the period and timing of the rotation pulse detected by the rotation speed detection means, and is optimal for the induced voltage of the rotor magnet of the rotor. By selecting the energization width, a drive device with high motor efficiency can be realized.

  In particular, when the induced voltage of the rotor is a trapezoidal wave, energization is performed in accordance with the trapezoidal wave, increasing the utilization of the induced voltage and lowering the switching loss than the sine wave, thereby increasing the efficiency of the motor. be able to.

  Hereinafter, a driving device 12 for a motor 10 according to an embodiment of the present invention will be described with reference to FIGS.

(1) Configuration of Motor 10 The motor 10 of the present embodiment is a three-phase brushless DC motor, and is used as a fan motor of an air conditioner, for example. The rotor of the motor 10 has four poles in which S poles, N poles, S poles, and N poles are alternately magnetized. The four-pole rotor magnet is magnetized so that the induced voltage generated in the three-phase stator winding by the rotation of the rotor becomes a trapezoidal wave.

(2) Configuration of Drive Device 12 The drive device 12 includes an inverter circuit 14, an upper arm drive circuit 16, a lower arm drive circuit 18, a position estimation circuit 20, a 120-degree energization matrix circuit (hereinafter referred to as an energization circuit) 22, a trapezoidal wave A modulation waveform generation circuit (hereinafter referred to as a modulation waveform generation circuit) 24, a counter circuit 26, a trapezoidal wave generation circuit 28, a triangular wave oscillation circuit 30, a comparator 32, and a three-phase distribution circuit 34 are configured.

  The inverter circuit 14 has a configuration of a full bridge circuit in which switching elements (for example, MOS-FETs) and diodes connected in parallel are connected in series vertically and three sets thereof are connected in parallel. The inverter circuit 14 is supplied with a motor current from a DC motor power supply 36. Among the six switching elements of the inverter circuit 14, a control signal is output from the upper arm drive circuit 16 to the gate terminal of the upper switching element, and each switching element is turned ON / OFF. A control signal from the lower arm drive circuit 18 is output to the gate terminals of the lower three switching elements, and is turned ON / OFF.

  In order to detect the position of the rotor magnet of the rotor of the motor 10, three position detecting elements (for example, Hall elements) 38, 38, 38 are provided, and the three position detecting elements 38, 38, 38 The pulsed position signal is output to the position estimation circuit 20.

  Based on the position signals from the three Hall ICs, the position estimation circuit outputs a three-phase rotation pulse to the energization circuit 22 and the counter circuit 26.

  The energization circuit 22 outputs a rectangular wave energization wave to the modulation waveform generation circuit 24 based on the input rotation pulse so that an induced voltage is applied only for 120 degrees in electrical angle in order to energize the motor 10 by 120 degrees. To do.

  The counter circuit 26 counts the position of each phase based on the rotation pulse and outputs it to the trapezoidal wave generation circuit 28.

  The trapezoidal wave generation circuit 28 outputs a rising slope wave and a falling slope wave. This will be described in detail later.

  In the modulation waveform generation circuit 24, the amplitude is determined based on the speed command voltage input from the outside, and based on the energization wave input from the energization circuit 22 and the rising and falling ramp waves input from the trapezoidal wave generation circuit 28. Generate a trapezoidal wave of each phase.

  A triangular wave is input from the triangular wave oscillation circuit 30 to the negative terminal of the comparator 32 at a predetermined cycle, and a trapezoidal wave of each phase is input from the modulation waveform generation circuit 28 to the positive terminal of the comparator. A wave is generated and output to the three-phase distribution circuit 34.

  The three-phase distribution circuit 34 outputs a PWM modulation signal for the upper switching element to the upper arm drive circuit 16 based on the three-phase PWM modulation wave, and drives the PWM modulation signal for the lower switching element to the lower arm. Output to the circuit 18.

  The upper arm drive circuit 16 outputs a control signal for turning on / off the upper switching element based on the input PWM modulation signal.

  Similarly, the lower arm drive circuit 18 outputs a control signal to the lower switching element based on the input PWM modulation signal.

(3) Trapezoidal Wave Generation Method Next, a trapezoidal wave generation method will be described with reference to FIGS.

  FIG. 2 shows a waveform of a trapezoidal wave of one phase (for example, U phase).

  In FIG. 2, the vertical axis indicates the voltage value of the speed command voltage, and the horizontal axis indicates the electrical angle.

  In FIG. 2, the rising slope wave and the falling slope wave of the portion α are generated by the trapezoidal wave generation circuit 28. In this case, the cycle and timing of the rotation pulse output from the position estimation circuit 20 is counted by the counter circuit 26, and a ramp wave is generated so that the voltage rises between 0 degrees and 40 degrees in electrical angle in FIG. Then, a ramp wave is generated so that the voltage falls between 160 degrees and 200 degrees.

  In FIG. 2, the β portion of the trapezoidal wave is generated by the energization circuit 22 and rises at a position of 40 degrees in electrical angle based on the cycle and timing of the rotation pulse output from the position estimation circuit 20. A rectangular energization wave that falls at a position of 160 degrees is generated. That is, a 120-degree energization waveform is generated.

  The modulation waveform generation circuit 24 combines the rising slope wave and the falling slope wave input from the trapezoidal wave generation circuit 28 and the energization wave input from the energization circuit 22 to generate the trapezoidal wave shown in FIG. In this case, the amplitude of the trapezoidal wave is determined based on the speed command voltage input from the outside. That is, the higher the speed command voltage, the higher the amplitude of the trapezoidal wave.

  It should be noted that the falling and rising electrical angle widths generated by the trapezoidal wave generation circuit 28 may be determined in the range of 10 to 60 degrees. This inclination angle is preferably obtained experimentally based on the characteristics of the rotor of the motor 10 or the like.

  As described above, a trapezoidal wave is generated based on the rotation pulse.

(4) Comparison between this embodiment and prior art Next, based on FIG. 3, the effect of this embodiment is demonstrated, comparing this embodiment with a prior art example.

  The upper part of FIG. 3 shows a three-phase rotation pulse, the middle part shows a three-phase energization wave of 120-degree energization in the conventional example, and the lower part shows a three-phase trapezoidal wave of this embodiment.

  The three-phase rotation pulse is, for example, a U-phase rotation pulse HU that is at a low level at 0 degrees and a high level at 180 degrees, that is, switches every 180 degrees.

  In the conventional example, energized waves U, V, and W of the upper switching element are generated based on the three-phase rotation pulse, and X, Y, and Z of the energized waves of the lower switching element are generated.

  In the present embodiment, trapezoidal waves U, V, and W of the upper switching element are generated, and trapezoidal waves X, Y, and Z of the lower switching element are generated.

  When the rectangular energized wave of the conventional example is compared with the trapezoidal wave of the present embodiment, the induced voltage is effectively used only at the rising and falling slope portions, and the utilization factor can be increased. Further, since the falling and rising are not steep as in the case of a rectangular wave, torque ripple does not occur. Further, since the induced voltage of the rotor of the motor 10 is a trapezoidal wave, energization is performed in accordance with the trapezoidal wave, so that the utilization rate of the induced voltage is increased and the switching loss is lower than that of the sine wave. Efficiency can be increased.

(Example of change)
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist thereof.

(1) Modification 1
In the above-described embodiment, 120-degree energization is performed, but 150-degree energization and 180-degree energization can be performed instead.

  However, when 150-degree energization is performed, the electrical angle obtained by adding up the rising slope wave, the energization wave, and the falling slope wave is set to be within 180 degrees.

  Further, in the 180-degree energization, the energization width is 180 degrees. Therefore, ramp waves are provided at the rising and falling portions of the 180-degree energization width so that the energization is 180 degrees as a whole.

(2) Modification example 2
In the above embodiment, the position of the rotor is detected by the position detection element. Instead, the induced voltage of each stator winding is detected, and the number of rotations is detected based on the detected induced voltage of each phase. It may be a sensorless circuit.

(3) Modification 3
In the above embodiment, the rotor magnet of the rotor is magnetized so that the induced voltage with respect to the three-phase stator winding becomes a trapezoidal wave. Can be raised.

  The brushless DC motor drive device of the present invention is suitable for household appliances, for example, a drive source of an air conditioner.

It is a block diagram of the drive device of the brushless DC motor which shows one Embodiment of this invention. It is a wave form diagram of a trapezoid wave modulation waveform. It is a wave form diagram which shows the three-phase rotation pulse, the three-phase energization wave of 120 degree energization of a prior art example, and the three-phase trapezoid wave of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor 12 Drive apparatus 14 Inverter circuit 16 Upper arm drive circuit 18 Lower arm drive circuit 20 Position estimation circuit 22 Current supply circuit 24 Modulation waveform generation circuit 26 Counter circuit 28 Trapezoid wave generation circuit 30 Triangular wave oscillation circuit 32 Comparator 34 Three-phase distribution circuit 36 Motor power supply 38 Hall IC

Claims (6)

An inverter circuit for supplying drive current to the three-phase stator winding of the three-phase brushless DC motor;
A rotational speed detection means for detecting the rotational speed of the rotor of the brushless DC motor;
Control means for outputting a control signal to the inverter circuit based on a rotation pulse period from the rotation speed detection means and a speed command signal from the outside,
In the drive device of the brushless DC motor having
The control means includes
An energization circuit that generates an energization waveform that is a rectangular wave based on the period and timing of the rotation pulse;
A trapezoidal wave generating means for generating a rising ramp wave and a falling ramp wave based on the period and timing of the rotation pulse;
A trapezoidal modulated wave generating means for generating a trapezoidal wave by combining the rising ramp wave, the energization wave, and the falling ramp wave, determining an amplitude according to the speed command signal;
A triangular wave oscillation circuit that oscillates a triangular wave at a predetermined period;
A PWM modulation circuit that generates a PWM modulated wave from the trapezoidal wave and the triangular wave;
A drive circuit for generating the control signal based on the PWM modulated wave;
A drive device for a brushless DC motor, comprising: The drive device for a brushless DC motor according to claim 1, wherein the rotor magnet of the rotor is magnetized so that the induced voltage of the rotor of the brushless DC motor becomes a trapezoidal wave. The energization circuit is
The brushless DC motor drive device according to claim 1, wherein 120-degree conduction, 150-degree conduction, or 180-degree conduction is performed. 2. The driving device for a brushless DC motor according to claim 1, wherein widths of the rising slope wave and the falling slope wave each have a width between 10 degrees and 60 degrees in electrical angle. The rotation speed detection circuit includes:
A position detection element in the vicinity of the rotor of the brushless DC motor;
The brushless DC motor drive device according to claim 1, wherein the rotational speed is detected based on a position signal from the position detection element. The rotation speed detection circuit includes:
The brushless DC motor drive device according to claim 1, wherein an induced voltage of each stator winding is detected, and the number of rotations is detected based on the detected induced voltage of each phase.

Images